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October 2000 3 <br />• the tape, in a laboratory grade, non-phosphate detergent (such as AlconoxT'" <br />or LiquinoxT"'~; <br />- Rinse with tap water (intermediate rinse); and <br />- Rinse the washed instrument with reagent grade deionized water. <br />If the electronic water level indicator becomes defective during sampling activities, a reserve <br />electronic water level indicator will be used to determine water levels. Any such replacement <br />equipment shall be decontaminated using the same procedures used to decontaminate the <br />primary electric water level indicator. <br />Water levels will be measured at each sampling point immediately prior to purging. Water <br />levels will be measured with a precision of ± 0.01 foot at each well's specified reference <br />point. Each monitoring well will have a reference point marked with a notch on the north side <br />at the top of the riser. The elevation of this point will be established by a professional land <br />• surveyor registered in the State of Colorado. <br />2.3 Sampling Order <br />The sampling order for each event shall begin with the well exhibiting the highest groundwater <br />elevation above mean sea level (MSL) and proceed in order of decreasing groundwater <br />elevation, ending with the well exhibiting the lowest groundwater elevation above mean sea <br />level. If contamination is believed to be present (i.e., if a statistically significant increase has <br />occurred in one or more wells), the sampling order will proceed from historically clean wells <br />to potentially impacted wells. <br />2.4 Purging <br />Purging and sampling equipment will consist of either bailers or pumps. The bailers may be <br />• either dedicated or disposable bailers, and the pumps may be either re-useable pumps to be <br />I:\ON2191\2191Gw5AP0.EV1009.DGC Sedalia Retrcling Center and Depository <br />